The invention relates to a chipping tool with a holder, slit in a fork-like fashion, for the clamping of a cutting insert, in particular to a recessing tool with the holder plate slit in a fork-like fashion and with the clamping slit formed in such a way that the jaws hold the cutting insert with a predetermined clamping force.
Similar recessing tools, especially recessing tools known as grooving tools, have previously been formed in such a way that the holding portion of the cutting insert is pushed in loosely from the front, having a minimal fitting insert, into the clamping slit of the holder plate. This obviously results in a very insufficient holding effect. In a different embodiment of such a self-clamping system with strongly conical formation and without a fixed contact point, the result is a tool which is basically only suited for grooving but not for recessing. Because of the wedge shape, the material expands so that neither an exact height setting nor a precise repetition accuracy is assured.
It is thus the object of the invention to produce a recessing tool which is easy to manufacture, and with the mounting system of the cutting insert allowing an exact, repetitious accurate holding at predetermined clamping force as well as under actual clamping conditions without having to fear that the cutting insert will be pushed out from the forks of the holding plate.
In order to accomplish this object, a tool of the initially described type has an insert limit contact point for the cutting insert and/or for the upper clamping jaws so that the cutting pressure leads to a proportional increase of the clamping tension.
This feature distinguishes the object of the invention from the prior art (compare, for example, German Pat. Nos. 31 33 029, 23 05 111, and 22 06 654) in which an insert limit contact point, if at all present, is arranged on the lower clamping jaws so that the cutting powers lead to no change in the clamping tension. Extensive experiments forming the basis for the present invention, have now shown that only by the increased clamping power caused by the cutting pressure is a really effective holding possible under hard operational requirements which manages without the need for additional screw clampings and at the same time allows an extremely easy loosening and exchange of the cutting inserts.
The clamping slit can be formed in such a way that the jaws of the holding plate hold the cutting inserts by a tool in an expandable fashion at a preset clamping tension. Providing a clamping slit, which has a normal resting position opening which is smaller than the clamping part of the cutting insert to be held, in combination with its expandability, which can be particularly favorably achieved by providing an essentially oval slit area for the insertion of a corresponding key, leads to a really solid holding of the cutting insert, which is sufficient even under unfavorable working conditions so that not only a grooving and a recessing tool is possible, but also a chipping tool with cutting plates clamped in this manner.
An additional embodiment of the invention provides for the clamping areas of the expandable upper leg in the working position ascending slightly inwardly, when compared to the clamping area of the cutting insert, which can be most easily accomplished when the clamping surfaces of the holding plates are formed in a backward, preferably parallel fashion, to one another, or slightly converge; however, in any case converge less than the clamping surfaces of the cutting inserts.
This latter embodiment, in which the converging formation of the clamping area has been chosen at the cutting body in order to achieve the actual clamping point at a considerable distance from the back end of the cutting insert, enables an essentially simpler working in of clamping areas of the clamping legs of the holder plate, which run parallel to one another, compared to the provision of backward diverging clamping areas in the holder plate, which would lead to the same effect.
In order to achieve a stable hold against transverse forces, it is an additional characteristic of the present invention to have at least the clamping surfaces of at least one of the clamping jaws correspond to a preferably triangular indentation or arching for the formation of the adjacent clamping surfaces of the cutting insert. By double prismatic formation of the holding segment, or reversely, by triangular grooves in the clamping areas of the cutting insert, opposite to one another, particularly good hold and security can be established against transverse stress.
The expandable upper clamping jaws can, according to the invention, be formed by a spring slit of the holding plate above the clamping slit, which enables the fastening of such cutting inserts by a simple holding at any point on a relatively large plate. This design is particularly suited for rotating tools, for example, saw blades with loosely inserted tempered cutting inserts forming the cutting ends.
It is further within the framework of the invention to push the expandable upper clamping jaw against the lower clamping jaw by a clamping screw. Besides the simplest type of expansion, which is, however, only possible in relatively thick holding plates in which the clamping screw transversely intersects both clamping jaws, a construction is possible, which is very favorable, and in which the clamping screw, having a conical head, can be inserted into the screw head of a spring slit which is essentially parallel and inclined towards the clamping slit. When screwing in the clamping screw, the conical head expands the spring slit and thereby pushes the expandable upper clamping leg against the rigid lower clamping leg of the holding arrangement according to the invention.
The insert limit contact point, so important for the invention, which assures increased clamping power at increased cutting pressure, can preferably consist of a contact angle, related to the jaw, and essentially L-shaped, onto which the cutting insert rests with its back side. In order to be able to use it even under the most extreme conditions, for example, when inserting the clamping holder, according to the invention, for saw blades with clamped cutting inserts, which rotate with more than ten thousand turns, without running the risk of the cutting inserts being hurled out, an additional embodiment of the invention provides for the cutting plate having a recess on the bottom side to receive a safety cam or pin located above the bearing surface area of the lower jaw. Such a safety cam or pin assures, even in the most unfavorable case of loss of clamping tension, that the cutting insert is not hurled out of its mounting.
In order to assure a simple insertion of the cutting insert in spite of this safety cam, an additional embodiment of the invention provides for the back lower corner of the clamping portion to have a rounding. This enables an angular insertion of the cutting insert between the jaws, without the need for a particularly strong tool expanding the jaw. This has the great advantage that the cutting inserts can be easily pushed into the mounting from the front without the need for special tools. Only the loosening requires the use of a screwdriver or a similar tool in most cases to lift the upper jaw.
It was initially mentioned in connection with the holder for the cutting insert that the holder was slit in a fork-like fashion. This, however, does not mean that the holder with its two jaws has to be a one-part component. It is on the contrary possible--and this in turn allows the mounting of any shape cutting plates for milling or chipping tools of all types--to form the upper jaw with the insert limit contact point as a component, which is loosely mounted in the recess of a holder, the one sidewall of which forming the lower jaw. In heavy metal cutting, there is always the danger of the jaw being destroyed as well, leading, in the case of multiple tools, to the entire tool becoming unusable. The possibility of exchanging the upper jaw, which is a loosely mounted separate component, effectively alleviates this problem. Furthermore, it also eliminates the metal cutting difficulties which would arise if split mounting plates were not used as in recessing tools, but wide holders for the insertion of large cutting plates.
For the fastening of the previously-mentioned component, the bearing portion of the component, which is fastened to the holder with one single mounting screw, can have an opening, preferably open towards the bottom, for a tilt-stop arrangement which engages into the opening. This enables the simple insertion of the component into the opening of the holder from the side, and in spite of using only one fastening screw, the longitudinal axis of the jaws cannot be tilted since the tilt-stop contact point, which can be in the form of a cross pin, creates a second distanced fastening point.
The lateral bearing for the cutting plate can be provided in the recess of the holder or formed on or in the upper jaw.
This last arrangement of the bearing on the upper jaw has the advantage that any shape cutting plates can be clamped into the same basic holder, provided that a suitable component is used, forming the upper jaw. Furthermore, this enables the use of tensioning elements for the mounting of triangular plates and plates of still more complex shapes.
In order to achieve the desired initial clamping tension in the mounting of cutting plates, according to the invention, these should on their upper side have an elevation forming a sliding ramp. The sliding ramps of the elevation provide the automatic expansion of the upper jaws when pushing or striking in the cutting plates which, of course, analoguous to the above-described cutting inserts, can have an opening on the bottom side for a safety cam in the bearing surface area.
The very narrowly built recessing tools of the invention are also very suitable for the construction of multiple tools. In this connection, several holding plates with clamped in cutting inserts are held parallel to one another by using gage block-like distancing pieces in a holding recess of a holder, with the mounting frame overlapping the plate package from above and the sides, the mounting frame being mounted in turn through a clamping wedge.
According to a particularly favorable embodiment, two holder plates, which according to the previously-described holding system have cutting inserts, run parallel to one another, and have their holding plates projecting forward with their clamping portion with adjusting arrangements provided in the area of the free end of the holder plates for the decrease and/or increase of the holder plate distance.
This changing of the holder plate distance enables the simple fitting of commercial regulating plates, eliminating the need for the production of a recessing slit of predetermined width to provide a correspondingly wide cutting tool. This is very circumstantial, especially in the case of non-standard widths, when special cutting inserts have to be provided. Further, the construction according to the invention provides for a continuous, very simple regulation during the unavoidable wear and tear of the cutting inserts as to the desired gage block.
The regulation arrangement of the invention can be most simply realized by providing expansion screws, which can be screwed into a first holder plate, supported by a second, and with additional counterscrews intersecting the first holder plate and being screwed into the second holder plate. By such expansion and counter screws, the holding plates can be brought close to one another or placed at a distance from one another so that together with a simple applied slide rule, a desired adjustment or regulation can be accomplished with few manipulations.
Additional advantages, characteristics and details of the invention can be found in the subsequent description of an embodiment as well as from the drawings.